Add user_agent option

Currently doesn't apply to requests made by youtube-dl as I
couldn't see a thread-safe way of doing that.

brozzler/browser.py

@@ -229,6 +229,7 @@ class Browser:
 
     def browse_page(
             self, url, extra_headers=None, behavior_parameters=None,
+            user_agent=None,
             on_request=None, on_response=None, on_screenshot=None,
             on_url_change=None):
         """
@@ -243,6 +244,7 @@ class Browser:
             raise BrowsingException("browser has not been started")
         self.url = url
         self.extra_headers = extra_headers
+        self.user_agent = user_agent
         self.on_request = on_request
         self.on_screenshot = on_screenshot
         self.on_url_change = on_url_change
@@ -460,6 +462,9 @@ __brzl_compileOutlinks(window).join(' ');
         if self.extra_headers:
             self.send_to_chrome(method="Network.setExtraHTTPHeaders", params={"headers":self.extra_headers})
 
+        if self.user_agent:
+            self.send_to_chrome(method="Network.setUserAgentOverride", params={"userAgent": self.user_agent})
+
         # disable google analytics, see _handle_message() where breakpoint is caught "Debugger.paused"
         self.send_to_chrome(method="Debugger.setBreakpointByUrl", params={"lineNumber": 1, "urlRegex":"https?://www.google-analytics.com/analytics.js"})
 

brozzler/job.py

@@ -85,7 +85,8 @@ def new_job(frontier, job_conf):
                     "enable_warcprox_features"),
                 warcprox_meta=merged_conf.get("warcprox_meta"),
                 metadata=merged_conf.get("metadata"),
-                remember_outlinks=merged_conf.get("remember_outlinks"))
+                remember_outlinks=merged_conf.get("remember_outlinks"),
+                user_agent=merged_conf.get("user_agent"))
         sites.append(site)
 
     # insert all the sites into database before the job

brozzler/job_schema.yml

@@ -64,6 +64,9 @@ id:
   metadata:
     type: dict
 
+  user_agent:
+    type: string
+
 seeds:
   type: list
   schema:

brozzler/robots.py

@@ -42,6 +42,8 @@ def _robots_cache(site):
             req_sesh.proxies = {"http":proxie,"https":proxie}
         if site.extra_headers():
             req_sesh.headers.update(site.extra_headers())
+        if site.user_agent:
+            req_sesh.headers['User-Agent'] = site.user_agent
         _robots_caches[site.id] = reppy.cache.RobotsCache(session=req_sesh)
 
     return _robots_caches[site.id]

brozzler/site.py

@@ -91,7 +91,8 @@ class Site(brozzler.BaseDictable):
             enable_warcprox_features=False, reached_limit=None,
             status="ACTIVE", claimed=False, start_time=None,
             last_disclaimed=_EPOCH_UTC, last_claimed_by=None,
-            last_claimed=_EPOCH_UTC, metadata={}, remember_outlinks=None, cookie_db=None):
+            last_claimed=_EPOCH_UTC, metadata={}, remember_outlinks=None,
+            cookie_db=None, user_agent=None):
 
         self.seed = seed
         self.id = id
@@ -111,6 +112,7 @@ class Site(brozzler.BaseDictable):
         self.metadata = metadata
         self.remember_outlinks = remember_outlinks
         self.cookie_db = cookie_db
+        self.user_agent = user_agent
 
         self.scope = scope or {}
         if not "surt" in self.scope:

brozzler/worker.py

@@ -260,6 +260,7 @@ class BrozzlerWorker:
                 browser.start(proxy=self._proxy(site), cookie_db=site.cookie_db)
             outlinks = browser.browse_page(
                     page.url, extra_headers=site.extra_headers(),
+                    user_agent=site.user_agent,
                     on_screenshot=_on_screenshot,
                     on_url_change=page.note_redirect)
             return outlinks

job-conf.rst

@@ -168,6 +168,18 @@ ignore_robots
 If set to ``true``, brozzler will happily crawl pages that would otherwise be
 blocked by robots.txt rules.
 
+user_agent
+----------
++-----------------------+---------+----------+---------+
+| scope                 | type    | required | default |
++=======================+=========+==========+=========+
+| seed-level, top-level | string  | no       | *none*  |
++-----------------------+---------+----------+---------+
+The ``User-Agent`` header brozzler will send to identify itself to web servers.
+It's good ettiquette to include a project URL with a notice to webmasters that
+explains why you're crawling, how to block the crawler robots.txt and how to
+contact the operator if the crawl is causing problems.
+
 warcprox_meta
 -------------
 +-----------------------+------------+----------+---------+